Study on microstructure and corrosion resistance of CoCrFeNiCuTi_x high-entropy alloy

The CoCrFeNiCuTi_x(_x = 0.25, , 0.50, 0.75, 1.00 by molar) high-entropy alloys (HEAs) were prepared by vacuum hot-pressing sintering in this paper. The effects of Ti contents on the microstructure and corrosion resistance of the CoCrFeNiCuTi_x HEAs were investigated and analyzed by optical microscope (OM), X-ray diffractometer (XRD), scanning electron microscope (SEM), HVS-1000B digital microhardness tester, and electrochemical workstation. The results show that the CoCrFeNiCuTi_x HEAs with different Ti contents by molar have the face-centeredcubic phase structure with the dendritic crystal microstructures. With the increase of Ti content, the dendritic structure declines in numbers, and the hardness of CoCrFeNiCuTi_x HEAs increases first and then decreases; the microhardness of the prepared HEAs reaches the maximum up to HV 755 at x=0.5. The self-corrosion potential of the prepared HEAs is positive to that of 45# steel; with the increase of Ti content by molar, the self-corrosion potential of the prepared HEAs increases first and then decrease, and the best corrosion resistance is obtained at x=0.5.